1. Field of the Invention
The present invention relates to a flip chip package, and more particularly to a flip chip package with an anti-floating structure, which facilitates the solder to connect the bumps of a flip chip with a leadframe.
2. Description of the Related Art
In the recent development of packaging technique, the flip chip package has become the current focus. A conventional flip chip package is used to flip-chip bond a chip to a leadframe, so as to reduce the package cost. As disclosed in ROC Patent Publication No. 567598, entitled “Flip Chip Package of Semiconductor Chips”, it comprises a leadframe, a semiconductor chip, a plurality of first bumps, and a plurality of second bumps. The leadframe comprises a die pad and a plurality of leads. The semiconductor chip comprises an active surface and a back surface opposite to the active surface on which a plurality of first solder pads and second solder pads are formed. The first bumps and the second bumps are disposed on the corresponding first solder pads and second solder pads respectively, so that the semiconductor chip becomes a flip chip. The semiconductor chip is arranged with the active surface facing the leadframe, and the first bumps and the second bumps are connected to the die pad and the leads, respectively. However, since the first bumps and the second bumps are low temperature eutectic bumps so as to be soldered to the leads, when they are soldered to the die pad and the leads, the leads of the leadframe do not have a solder mask to define the soldering area, and the heights of the first bumps and the second bumps will thus be affected by collapse and diffusion.
Referring to FIGS. 1 and 2, another conventional bonding method that is to bond the high-temperature bumps of a flip chip to a leadframe through the solder is disclosed. The conventional flip chip package 100 mainly comprises a leadframe 110, a flip chip 120, and a plurality of eutectic solders 130. The leadframe 110 comprises a plurality of leads 111 that comprise the eutectic solders 130 formed beforehand. The flip chip 120 comprises a plurality of high temperature bumps 121, e.g., high lead bumps, such as lead/tin 95/5, so that the high lead bumps 121 will not be melted during reflowing of the eutectic solders 130, thus avoiding the collapse and diffusion of the bumps 121. Referring to FIG. 2, the eutectic solders 130 are used for soldering the high temperature bumps 121 of the flip chip 120 to the leads 111 of the leadframe 110. During the process of reflowing, the flip chip 120 may always float up because of the surface tension of the eutectic solders 130, such that the solders 130 may form a necking portion 131 at one side near the leadframe 110 after reflowing. Therefore, the stress is easily concentrated on the necking portion 131, which may easily break off.
Consequently, there is an existing need for a flip chip package with an anti-floating structure to solve the above-mentioned problems.